Method of turning grooves

Abstract

A method of turning very small grooves into a hardened steel work piece using a precision or ultraprecision lathe. Positioning of the work piece on the lathe spindle and dressing the work piece to minimize runout, aligning the cutting tool with the face of the work piece to be grooved, the lathe cutting speed and the cutting tool feed rate are all precisely controlled in order to maintain the forces acting on the cutting tool to levels below which fracture of the tool will occur. The cutting tool has a specially configured tip of a cubic boron nitride material.

I claim: 
     
       1. A method, using a precision or ultraprecision lathe, of lathe turning a groove (13) into a circumferential surface (11) of a hardened tool steel workpiece (10) that has been mounted on said lathe and dressed so as to eliminate, within the tolerance limits of said lathe, runout, comprising the steps of selecting a cutting tool (40) having a longitudinal axis (A) and a cutting tip (46) comprised of a cubic boron nitride material according to the criteria (a) if said hardened tool steel contains relatively large carbide particles (on the order of 25 to 50 microns), select a cutting tip having a cubic boron nitride material having high fracture toughness and     (b) if said hardened tool steel contains relatively smaller carbide particles (less than 25 microns), select a cutting tip having a cubic boron nitride material having high hardness and wear resistance;   forming said cutting tip to a shape suitable to cutting said grove;   aligning said cutting tool with said circumferential surface so that said longitudinal axis is precisely perpendicular to said circumferential surface;   setting the rotational speed of said workpiece so that the linear velocity of a point on said circumferential surface is between 80 and 200 meters per minute; and   cutting said groove into said circumferential surface at a tool feed rate of between five and 20 microns per revolution of said workpiece.   
     
     
       2. The method of claim 1 where said linear velocity is 160 meters per minute. 
     
     
       3. The method of claim 1 where said tool feed rate is 20 microns per revolution.